This invention relates to a vertical die casting machine.
Although a vertical die casting machine has an excellent characteristic, its application is limited due to its construction, especially by the fact that it includes a number of component parts which are difficult to maintain in good operating condition. Thus, according to one prior art vertical die casting machine, once set on a stationary platen, the casting sleeve and the stationary or lower die cannot be readily removed except when replacing these members so that it is necessary to teem molten metal through the parting plane of the upper and lower dies. Accordingly, overflown molten metal or foreign matter tends to accumulate in the lower die, thus damaging the same. Moreover, as it is necessary to clean the dies and to apply a lubricant before teeming, and to clamp the dies and insert a core after completion of the teeming, the time of the operating cycle is prolonged. Consequently, the temperature of the molten metal decreases, thereby degrading the quality of the cast product.
Considering the relationship between the operation cycle time and the temperature of the molten metal, there are two contradictory relationships, that is, in order to improve the quality of the product, the temperature of the molten metal should be high; whereas to improve the production speed, it is necessary to decrease the temperature of the molten metal so as to accelerate the solidification thereof.
In other words, where high quality is important, on the one hand, the productivity is left out of consideration; and where the productivity is important, on the other hand, the quality is degraded. Such contradictory conditions are inevitable in a vertical die casting machine. According to a prior art design, however, a preference is given to the productivity and therefore, for the purpose of preventing an excessive temperature rise of the casting sleeve, means for cooling the entirety of the same has been provided. In consequence, the solid phase of the molten metal increases, thus degrading the quality of the product.